Activated sludge purification of sewage and other liquids



ACTIVATED SLUDGE rfifiimcmlon 0F SEWAGE-AND OTHER LIQUIDS Filed Aug. 27, 1936" 2 Sheets-Sheet l ISTREANDER INVENTQR Philip B. Sh'eander ,Ka ATTORNEY ,1938; P. a. STREANDER 2,126,228

ACTIVATED SLUDGE. PURIFICATION OF SEWAGE AND OTHER LIQUIDS Filed Aug. 27, 1956 2 Sheets-Shet 2 gay. 2.

wa 95 E 5% ff- UH INVENTOR Philip Sfreander Patented Aug. 9, 1938 UNITED stares 2.12am Ac'rrvs'ran stones Pmlll-JICATIDN or s waa sun ornaa HQUES Philip lit. Streander, Maplewood, N. 3., assignor to Municipal Sanitary service Gorporation, New lion-MN. h... a corporation ed New York Application August at, 1936, Serial No. 98,118 6 Claims. (El. 210-8) The present invention relates to the purification of sewage and other impure liquids by the use of activated sludge. This purification is effected by the action of aerobic bacteria stimul5 lated by aeration of the sewage which tends to keep the bacterial sludge well distributed and- 1 Preferably between 10 and 30 per cent of the activated sludge settling out in the final settling tering the aeration tank.

During thefirst stages of the aeration period '2 the impurities in the sewage are rapidly coagulated and adsorbed by the activated or biologically active sludge, and the rate of coagulation and adsorption is proportional to thepercentage of biologically active sludge in the sludge liquor. 25 In the latter stages, purification proceeds at a much slower and uniform oxygenation of the mixing liquor. During this stage the presence of a large proportion of sludge retards the oxygena-' tion of the sewage proper. 30 The principal object; of the present invention are to provide improved apparatus and methods for activated sludge purification of sewage and analogous liquids.

According to a preferred manner of carrying 35- out the invention, the activated sludge treatment may be effected in a singletank and in such a manner that the heavy concentration of returned sludge is always at the influent end of the tank and available for the first stages of aeration.

40 This condition is obtained by providing conveying means acting to carry the heavier sludge particles to the influent end or the tank and mix them with the incoming raw sewage.

The structure maybe so arranged and the 45 air so introduced as to produce a transverse or lateral movement of the liquid and even a rotating movement thereof. Also by varying the amount of air introduced at different points the rotation may be varied at different parts. For 50 example there may be a higher rate of rotation at the influent end and alower rate at the eiliuent end, thereby at last partially obtaining a selective graduation of theparticles settling to the bottom of the tank. The transverse velocities 55 with the preferred form of tank may be consid-' tank is returned to and mixed with sewage en erably lower than for the conventional type of tank, particularly in the latter half of the tank. The efliuent from this type of aeration tank will consist of the lighter forms of activated sludge and may be disposed of in any suitable manner. Under certain conditions it may be desirable to collect smaller particles of activated sludge and convey them to the'influent end of the tank.

Other objects, features'and advantages will be apparent upon consideration of the following description and of the drawings in which:

Fig. 1 is a vertical longitudinal section of one 7 unit constituting a preferred embodiment oi the invention;

"Fig. 2 is a section on the line 2-2 of Fig. l; and

Fig. 3 is a section on the line 3-3 of Fig. l. Reierrlng to the drawings, the liquid to be treated may be supplied through a conduit or pipe it to a distributing chamber ii mounted on the end wall it of a. tank it. The distributing chamber ll may have an inclined bottom direct ing the liquid through slots or openings I l into the tank is substantially below the normal liquid level. After aeration in the tank it the eflluent -may pass'out through outlets or slots it into a chamber It supported on the other end well ill of the tank. The chamber it may be provided with a weir vIl which determines the normal height of the liquid in the tank andover which the liquid flows for discharge into an .eiiiuent duct or conduit 18.

Aeration of the liquid passing through the tank It may be effected in different ways but preferably by means'of air difiusers or suppliers I9 arranged along the side walls 2|! and 2| of the tank in air-lift channels 22 between the walls 20 and 2| and upright bailies 23.- It will be seen that the liquid passing upwardly through. the air-lift channels tends to flow inwardly toward 40 the middle of the tank and then downwardly to the lower part of the tankwhere it is again drawn beneath the bailies 23.

To effect a smooth flow of the liquid the side walls and bottom of the tank may be connected in such a way as to provide curved deflecting surfaces, and the walls may be shaped near their tops so as .to provide suitably curved deflecting surfaces to direct the liquid toward the middle of the tank. The control of the flow of liquid at the top of the tank may also be assisted by I providing curved plates or deflectors 24 at the upper edges of the baflies 23. Proper circulation of the liquid mayalso be facilitated by a double deflector 25 located longitudinally and centrally 2 of the tank in the upper part thereof and supported by suitable cross members 26 extending from one side of the tank to the other. Said defiector 25 is provided with curved deflecting surfaces at opposite sides to direct downwardly liquid passing from the sides of the tank and engaging the deflector. The air diffusers or sup pliers IB may be supportedln pairs at the lower ends of vertical pipes 21 connected at their upper ends' through valves 28 with air mains 29 preferably located immediately above the side walls -is carried to the influent end of the tank by a suitable conveyor-such as an open work endless conveyor comprising scrapers 30 mounted on flexible members or belts 3| passing over sprockets 32 and 33 respectively, rotatably mounted at the.

top and bottom of the tank and at its ellluent end. The belts 3| also pass around sprockets I4 rotatably mounted in the bottom of the tank near its influent end, sprockets 35 rotatably mounted at the influent end of the tank somewhat below the inlet l4 and positively driven sprockets 36 mounted at the top of the tank at the influent end at substantially the same level as sprocke 32 at the eiiluent end of the tank.

The sprockets "may be rigidly mounted on a shaft 31 which may be driven by means of a sprocket 38 fixed thereon and belt 39 connecting 'the sprocket 38 with the sprocket 40 mounted on a driving shaft, the driving shaft 4| being/prothe activated sludge conveyed to the influent end vided with a sprocket 41 which in turn is driven by a belt or chain 43 also passing around a sprocket 44 of driving mechanism 45. The arrangement of the sprockets is such that the scrapers '30 will carry settled sludge along the bottom of ,the tank toward the inlet end, up an incline 45 from the bottomof the tank to the front wall of the tank and then upwardly to the inlet l4. The upper reach of the endless conveyor may be supported by angles '41 receiving the ends of the scrapers 30.

The flow of the liquid through the tank may be controlled by a transverse partition 48 provided with slots.

, Preferably the bottom of the tank is provided with a sump or depression 50 having a flat bot-.

tom to cooperate with the scrapersand having sides of such inclination as to restrain sidewise movement of the settled sludge with the liquid flowing outwardly to the lower portions of the airlift channels.

In operation, the sewage to be treated flows through the inlet I4 into the tank It and due to the slotted partition 48 is thoroughly mixed with of the tank by the scrapers 30. Consequently during the early stages of the aeration period,- the impurities in the influent sewage are rapidly centage of biologically active sludge in the sludge liquor. Due to the air diffusers in the air lift channels between the bailies 23 and the sidewalls of the'tank, the material in the compartment set of! by the partition 40 is drawn out under the inclined lower edges of the adjacent portions of the baifles 2t and, aided by the various deflecting surfaces, flows in two substantially helical paths to the eiiluent end of the tank. During this flow through the tank the heavier particles will tend to settle first and the lighter ones later. It will be evident that, by regulation of the valves 24 the rate of rotation flow may be varied in different parts of the tank. By gradually reducing the rate of rotation toward the eiiiuent end of the tank, same selective graduation of the settled particles may be obtained.

It should be understood that various changes may be made and that various features may be used without others without departing from the true scope and spirit of the invention.

Having thus described my invention, I claim:

1. In a purification system, a tank having an inlet at one end wall and an outlet at the other end wall, aeration means acting on liquid passing through said tank, and means for moving all of the settled activated sludge back along the bottom of the tank to its inlet end and up the surface of the inlet end wall to the inlet for mixture with the influent liquid.

2. In a purification system, a tank having an inlet at one end and an outlet at the other end, means for aerating sludge passing through the tank, and means-for moving settled activated sludge to the inlet end of the tank for mixture with the influent liquid, said sewage aerating means including air supplying devices at the sides of the tank to cause upward flow of the liquid adjacent said sides, and a deflecting device at the L top of the tank and extending longitudinally and centrally-thereof to direct downwardly the liquid flowing upwardly at the sides of the tank and inwardly at the upper surface of the liquid in the tank.

3. In a purification system, a tank having an inlet at one end andan outlet at the other end, means for aerating the liquid passing through the tank and causing circulation transversely of the liquid flowing thereto from the sides of the tank.-

4. In a sewage purification system, a tank having an inlet at one end and an outlet at the other end, an upright home at each side of the tank and extending longitudinally thereof, aerating means including air supplying devices between the baiiies and the corresponding sides of the tank to cause upward flow of the sewage adjacent said sides, the bottom of the tank being provided with a longitudinal sump with sides spaced inwardly from the sides of the tank to a somewhat greater extent than said battles and serving to restrain activated sludge settled in said sump from being carried out of the same by liquid flowing toward the sides of the tank, and means for moving the settled activated sludge along said sump to the inlet end of the tank and up along the surface of said inlet end to said inlet for mixture with incoming sewage.

5. In a purification system, a tank having an inlet at one end, an outlet at the other end, a

bottom with a flat-bottomed sump from the sides oi! the tank and a curved extension. of the sump leading up to the inlet. means-for aerating verse perforated partition near the influent for mixture with the influent liquid, two upright baiiiles extending longitudinally of the tank adjaeent to the sides thereof, sewage aerating means including air supplying devices between the baifles and the sides oi the tank to cause upward flow oi the liquid adjacent said sides, and a trans;

of the tank and extending across the space between the bailies to provide a mixing chamber in which the activated sludge and incoming sewage are brouliht together.

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